Comparison of Methods for Estimating Critical Properties of Alkyl Esters and Its Mixtures

Abstract

Biodiesel is a renewable fuel which can be described chemically as a mixture of different alkyl esters. To predict its different thermophysical properties, critical properties (P c , T c , V c ) must be known or estimated. In this work, the use of group contribution and group interaction methods is compared regarding its goodness in the prediction of a widely measured property such as biodiesel density, as there is a lack of data of normal boiling point or densities of pure alkyl esters. The results show that a group interaction method, with the available data of 20 different biodiesels published, can predict better biodiesel density when methanol was used for the transesterification reaction. Data available for biodiesel produced with ethanol are scarcer; only six sets of biodiesel composition and density could be found, and in this case, both group interaction and group contribution methods predict density with a similar error, although more data are needed.

Prediction of Vapor Pressure of Fatty Acid Methyl Esters

“…al. [5] has discussed several models for prediction of such properties and divided them in three packages as shown in Table 2. We have used these packages to predict critical properties.…”

“…Therefore, ф L = ƒ L /P v = 1 and P v = ƒ L . The liquid phase fugacity ƒ 0 at low pressure (P → 0) is equal to the vapor pressure: P v ≈ ƒ 0 [5]. In this study, PR-EOS is used for the vapour pressure prediction of FAME at zero pressure fugacity.…”

Group Contribution Methods for Estimation of Selected Physico-Chemical Properties of Organic Compounds

“…They were developed to estimate, e.g. critical properties (Lydersen, 1955;Ambrose, 1978;Ambrose, 1979;Joback & Reid, 1987;Gani & Constantinou, 1996;Poling et al, 2001;Marrero & Gani, 2001;Brown et al, 2010;Monago & Otobrise, 2010;Sales-Cruz et al, 2010;Manohar & Udaya Sankar, 2011;Garcia et al, 2012), parameters of state equations (Pereda et al, 2010;Schmid & Gmehling, 2012), acentric factor (Constantinou & Gani, 1994;Brown et al, 2010;Monago & Otobrise, 2010), activity coefficients (Tochigi et al, 2005;Tochigi & Gmehling, 2011), vapour pressure (Poling et al, 2001;Miller, 1964), liquid viscosity (Joback & Reid, 1987;Conte et al, 2008;Sales-Cruz et al, 2010), gas viscosity (Reichenberg, 1975, heat capacity (Joback & Reid, 1987;Ruzicka & Domalski, 1993a;Ruzicka & Domalski, 1993b;Kolská et al, 2008), enthalpy of vaporization (e.g. Chickos et al, 1995;Chickos & Wilson, 1997;Marrero & Gani, 2001;Kolská et al 2005, etc.…”

“…Nikitin et al, 2010) and also for mixtures (e.g. Awasthi et al, 2010;Papaioannou et al, 2010;Teixeira et al, 2011;Garcia et al, 2012). Also e.g.…”

The New Method for Correlation and Prediction of Thermophysical Properties of Fluids. Critical Temperature

“…Owing to its powerful function of estimation, the GC method was widely used to estimate the T c of pure organic compounds, 12,13 ionic liquids, 14−18 and mixtures. 19 Quantitative structure property relationship (QSPR) 20−24 was also an effective approach for prediction of T c . It mainly explores quantitative relations between molecular structure and physicochemical properties of compound accurately using statistic and theoretical calculation.…”